EAS and RFID systems are typically utilized to protect and/or track assets. In an EAS system, an interrogation zone may be established at the perimeter, e.g. at an exit area, of a protected area such as a retail store. The interrogation zone is established by an antenna or antennas positioned adjacent to the interrogation zone.
EAS markers are attached to each asset to be protected. When an article is properly purchased or otherwise authorized for removal from the protected area, the EAS marker is either removed or deactivated. If the marker is not removed or deactivated and moved into the interrogation zone, the electromagnetic field established by the antenna(s) causes a response from the EAS marker. An antenna acting as a receiver detects the EAS marker's response indicating an active marker is in the interrogation zone. An associated controller provides an indication of this condition, e.g., an audio alarm, such that appropriate action can be taken to prevent unauthorized removal of the item to which the marker is affixed from the protected area.
An RFID system utilizes an RFID marker to track articles for various purposes such as inventory. The RFID marker stores data associated with the article. An RFID reader may scan for RFID markers by transmitting an interrogation signal at a known frequency. RFID markers may respond to the interrogation signal with a response signal containing, for example, data associated with the article or an RFID marker ID. The RFID reader detects the response signal and decodes the data or the RFID tag ID. The RFID reader may be a handheld reader, or a fixed reader by which items carrying an RFID marker pass. A fixed reader may be configured as an antenna located in a pedestal similar to an EAS system.
Historically, transmitting, receiving, or transceiver antennas in EAS and RFID systems have been configured as loop-type antennas. Recently, however, magnetic core antenna configurations have been explored for use in such systems. Materials utilized as the core material in core antennas have included ferrite and amorphous magnetic material.
Ferrite material may be provided as a powder, which is blended and compressed into a particular shape and then sintered in a very high temperature oven. The compound becomes a fully crystalline structure after sintering. Ferrite materials have a higher magnetic permeability than air, and have a relatively low saturation flux density compared, for example, to most amorphous materials. Also, ferrite materials that operate at higher RF (e.g. 15 MHz) frequencies have relatively low permeability and/or saturation flux density.
In contrast to ferrite materials, amorphous magnetic materials lack a distinct crystalline structure. Amorphous magnetic materials e.g., VC6025F available from Vacuumschmelze GmBH Co. (D-6450 Hanua, Germany), have been successfully utilized in lower frequency EAS applications, e.g., 58 kHz. However, such amorphous magnetic materials do not perform well in the RF frequency range as core loss and permeability decrease performance for frequencies higher than a few 100 kHz.
Accordingly, there is a need for a core antenna for EAS and RFID applications capable of suitable operation frequencies up to the RF range. In addition, there is a need for improved performance of a core antenna in the lower frequency range for EAS as an alternative to ferrite or amorphous materials.